The present invention relates to a numerical control system, and more particularly to a numerical control system in which a tool or a table can be manually moved as the tool axis direction of the tool relative to a workpiece is kept unchanged.
In a machine tool, for example, a machining center, a tool or a table is rotated in the directions of a B-axis (vertical rotational direction) and a C-axis (horizontal rotational direction) so as to control the axial direction of the tool relative to a workpiece (the axial direction being termed the "tool axis direction"), movement also occurs in the directions of the three X, Y and Z axes so as to subject the workpiece to a desired machining operation.
In forming a hole in the workpiece under such simultaneous 5-axis control, first of all, a tool holder is positioned by moving it in the X-, Y- and Z-axial directions unitarily with the tool, while the tool axis direction and the axial direction of the hole to be machined are brought into agreement by rotating the tool in the B-axial directions. Thereafter, while maintaining the tool axis direction, the tool holder is moved toward the workpiece by simultaneous 3-axis control of the X-, Y- and Z-axes. The machining of the hole is started, and the drilling operation is performed down to a predetermined depth. Lastly, the tool is drawn out in the direction opposite the machining to complete the drilling operation. This system has hitherto been proposed.
In the machine tool such as a machining center which conducts machining with the tool inclined relative to the tool holder, an operator may want .circle.1 to manually increase or decrease the depth of the cut in the course of the machining with the inclined tool, or .circle.2 to manually drill an inclined surface. Here, the expression "manual operation" signifies the function of moving the tool or the table by manually operating an ordinary manual pulse generator or jog button.
In the aforementioned cases .circle.1 and .circle.2 , the tool must be manually moved by the simultaneous 3-axis control of the X-, Y- and Z-axes as the tool axis direction of the tool is held in agreement with the direction of the hole.
In the manual operation of the prior art, however, the tool 12 (see FIG. 1), is moved in every axial direction by means of the manual pulse generator or the jog button, and the requirement in the cases .circle.1 and .circle.2 cannot be met.